Cognitive deficit is correlated with sleep stability in insomnia: A cardiopulmonary coupling study

Objectives To assess the correlation of cognitive function with sleep stability and depressive‐anxious symptoms in insomnia patients. Methods Twenty‐two insomnia patients with cognitive impairment (insomnia‐CI), 21 insomnia patients with normal cognition (insomnia‐CN), and 15 matched healthy control subjects (HCs) were enrolled and completed neuropsychological tests, the Hamilton Depression and Anxiety Scales (HAMD and HAMA), the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index (PSQI),the Insomnia Severity Index (ISI), and the cardiopulmonary coupling (CPC) examination. Ratios of high‐frequency coupling (HFC), low‐frequency coupling (LFC), and very low‐frequency coupling (VLFC) measured by CPC analysis represent stable sleep, unstable sleep, and wake/rapid eye movement (REM) sleep, respectively. Results The HAMD, HAMA, PSQI, and ISI scores were higher in the insomnia‐CN patients than in the HCs (all p